1. Field of Invention
This invention relates to coloring materials and, more particularly, to dyes of the anthraquinone class having alkylsulfonylamino substituents.
In the practice of the present invention, the term "sulfonylamino" is used to identify that the substituent is uniquely bonded to the ring through the nitrogen atom, i.e., RSO.sub.2 NH--. Although chemical nomenclature is clear on the point, the term "sulfonamido" is used in the literature to mean a substituent bonded either through the nitrogen (correct) or through the sulfur atom (incorrect) thus creating confusion. Similarly we have used the term "carbonylamino" to clarify the position with the carboxylic acid equivalents bonded through the nitrogen atom.
2. BACKGROUND OF THE ART
While many yellow, orange and red anthraquinone dyes are available, for example acylamino-substituted anthraquinones, there remains a need for improving properties other than purely optical and color considerations such as hue. The successful application of dyes to a variety of processes requires tailoring of properties other than color to the needs of the application. For example, for outdoor signs good weathering resistance of the dyes used is a prerequisite. In the production of colored coatings on objects, solubility of the dye in the coating medium is a key characteristic. For dyes incorporated in liquid crystal devices, a high order parameter is desirable. In thermal dye transfer imaging applications control of dye melting point is crucial to effective image formation. In fluorescent inks, the emission wavelength of the dye in relation to its absorption wavelength is an important criterion.
Anthraquinone dyes with acylamino substituents, free of auxochromic groups such as amino, alkoxy and alkylthio, are well known in the art. Acylamino groups of the alkylcarbonylamino and arylcarbonylamino variety are known, the latter in particular being common (e.g., CI 60520, CI 61650, CI 61725).
Anthraquinones substituted solely with arylsulfonylamino groups have also been reported. These are described, for instance, in: F. Ullmann, Ber., 43, 536 (1910); H. Kauffmann and H. Burckhardt, Ber., 46, 3808 (1913); F. Ullmann and G. Billig, Ann., 381, 11 (1911); R. Scholl et al., Ber., 62, 107 (1929); K. Naiki, J. Soc. Org. Synth. Chem. Japan, 13, 72 (1955); and in German Pat. No. 224,982 and U.S. Pat. Nos. 3,274,173 and 3,240,551. These are, in general, high melting, poorly soluble, rather intractable materials.
Anthraquinones have also been described in which arylsulfonylamino and arylcarbonylamino groups are simultaneously present. Such materials may be found in the aforementioned U.S. Pat. No. 3,240,551, in U.S. Pat. Nos. 1,939,218 and 1,966,125, and in German Pat. Nos. 623,069 and 647,406.
In view of the fact that anthraquinones substituted with alkylcarbonylamino groups have been known for over 100 years (see e.g., H. Roemer, Ber., 15, 1786 (1882)), it is surprising that the first simple alkylsulfonylaminoanthraquinone was reported only in 1986 in Japanese Kokai JP61-10549. That patent application claims, among other materials, anthraquinones bearing a single lower alkyl- or lower haloalkylsulfonylamino substituent, with an additional substituent in each outer ring selected from hydrogen, lower alkyl, lower haloalkyl or halogen. They are described as useful for their anti-inflammatory, antipyretic, analgesic and diurectic activity. These materials are stated to be prepared by reaction of an aminoanthraquinone with an alkanesulfonyl chloride in the presence of pyridine, as is known in the art. All the concrete examples of this patent involve either the methylsulfonylamino or the trifluoromethylsulfonylamino substituent. We have been able to prepare these same derivatives in good yield by the stated method. However, in work on the present invention, all attempts to prepare alkylsulfonylamino derivatives containing two or more carbon atoms by said method were, surprisingly, unsuccessful. This observation may be related to the intervention of sulfene intermediates in these types of reaction. (See, for example J. F. King, Acc. Chem. Res., 8, 10 (1975)). Whatever the cause, we have been able to prepare mono- and poly-alkylsulfonylamino derivatives with two or more carbon atoms only by other methods described in detail below, thus providing the first access to this class of materials. Additional art pertinent to these materials is U.S. Pat. No. 4,062,875, which describes a process comprising treating a 2-acylamino-2'-carboxydiphenylmethane with an acid condensing agent, whereby there is formed the corresponding 4-acylaminoanthrone, which may be oxidized to the corresponding anthraquinone. The patent does not, however, disclose any example of the process operated with an acyl radical derived from a sulfonic acid. U.S. Pat. No. 3,558,698 concerning N-substituted perfluoroalkanesulfonamides claims anthraquinonyl derivatives, among others. The example of 2-trifluoromethylsulfonylaminoanthraquinone is provided. This material is not a dye. In U.S. Pat. No. 3,278,549 there are disclosed water-soluble reactive dyes, exhibiting good wash fastness on cellulose and protein fibers, characterized by the presence of a 1,2,2-trifluorocyclobutyl group, optionally containing additional substituents. This group may be attached to a variety of dyes, including anthraquinone dyestuffs, by a range of amide links among which are --NHSO.sub.2 -- and --NHSO.sub.2 CH.sub.2 CH.sub.2 -- linkages. All the examples of anthraquinone dyes contain at least two --SO.sub.3 H groups, and contain the 1-amino and 4-anilino auxochromic groups. In the single instance of a --NHSO.sub.2 -- link this group is not attached to the anthraquinone nucleus, and the dye is blue.
U.S. Pat. No. 3,617,173 claims polyester fibers dyed with 2-aroylanthraquinones having various amino substituents in the 1- and 4-positions. The possibility of simultaneously included 1-arylsulfonylamino and 4-alkylsulfonylamino substituents appears to be considered, but no examples are provided of such materials. This is not surprising in view of the steric hindrance towards introduction of large 1-substituents presented by the 2-aroyl group. Indeed, all the samples in this patent contain either a simple amino or a methylamino group in the 1-position, reflecting the difficulty of synthesis of the above materials.
Although thermal printing of textiles bears a superficial resemblance to diffusive thermal dye imaging, in reality quite different processes with distinct properties and material requirements are involved. Thermal printing occurs by a sublimation process, so that substantial vapor pressure is a prime criterion for dye selection. In diffusive dye imaging, high vapor pressure of the dye contributes to undesirable thermal fugacity of the image. For the melt state diffusion process involved in this situation, melting point is instead a better basis for dye selection. Diffusive dye transfer is a high resolution dry imaging process in which dye from a uniform donor sheet is transferred in an imagewise fashion by differential heating to a very smooth receptor, using heated areas typically of 0.0001 square inches or less. In contrast, the thermal printing of textiles is of comparatively low resolution, involving contemporaneous transfer by uniform heating of dye from a patterned, shaped or masked donor sheet over areas of tens of square feet. The typical receptors printed in this manner are woven or knitted fabrics and carpets. The distinct transfer mechanism allows such rough substrates to be used, while diffusive imaging, where receptors with a mean surface roughness of less than 10 microns are used, is unsuitable for these materials. Unlike diffusive thermal dye imaging, the transfer printing process is not always a dry process; some fabrics or dyes require pre-swelling of the receptor with a solvent or a steam post-treatment for dye fixation. Though the transfer temperatures for the two processes can be similar (180.degree. to 220.degree. C.), diffusive dye transfer generally operates at somewhat higher temperatures. However, in a manner strikingly reflective of the differences in mechanism involved, diffusive dye transfer involves times of around 5 msec, whereas thermal printing normally requires times of 15 to 60 sec. In accord with the sublimation process involved, thermal printing often benefits from reduced atmospheric pressure or from flow of heated gas through the donor sheet. Thermal printing is a technology developed for coloring of textiles and is used to apply uniformly colored areas of a predetermined pattern to rough substrates. In contradistinction, diffusive dye transfer is a technology intended for high quality imaging, typically from electronic sources. Here, a broad color gamut is built with multiple images from donors of the three primary colors onto a smooth receptor. The different transfer mechanism allows the requirement for grey scale capability to be fulfilled, since the amount of dye transferred is proportional to the heat energy applied. In thermal printing grey scale capability is expressly shunned, because sensitivity of transfer to temperature decreases process latitude and dyeing reproducibility.
When auxochromic groups such as alkylthio, alkoxy, amino and substituted amino are introduced into the anthraquinone nucleus along with alkyl- or arylsulfonylamino groups, the resulting dyes are generally red, violet, or blue. Many examples of these dyes are known in the art. Typically, both aryl- and alkylsulfonylamino derivatives are claimed in the same patent, without any differentiation in properties. Examples of such materials are contained in U.S. Pat. Nos. 2,640,059, 3,394,133, and 3,894,060, wherein a single sulfonylamino substituent is present, and in U.S. Pat. No. 3,209,016 and Japanese Kokai 63-258955, wherein two sulfonylamino groups may be present. In other instances, alkyl- and arylsulfonylaminoanthraquinones of otherwise identical structure are claimed in separate patents, again with no distinction between the properties of the two classes. Thus, U.S. Pat. No. 1,948,183 claims 1-amino-2-alkoxy-4-arylsulfonylaminoanthraquinones, while U.S. Pat. No. 3,072,683 claims 1-amino-2-alkoxy-4-alkylsulfonylaminoanthraquinones.
As was stated previously, arylsulfonylaminoanthraquinones without auxochromic groups are rather intractable materials. In contrast, the new yellow, orange and red alkylsulfonylaminoanthraquinones of this invention are more valuable dyes by virtue of their increased solubility in non-aqueous solvents and reduced melting points, which render them more useful for a variety of applications. Despite the absence of the arylamide groups usually associated with good fading resistance, these dyes provide excellent photostability.